If you write content in the first line above the default Microsoft email signature, the recipient will not see the content.
It's difficult to add content by mistake in the first line above the email signature.
When you click to add the body text, you will always enter the second line, and there are no problems.
You must click twice to enter the first line above the email signature.
We designed the server-side method to look for the HTML tag and replace everything inside.
The Outlook app includes the first line inside the HTML tag:
<html> <br />THIS TEXT WILL NOT SHOW AT THE RECIPIENT END <br />Get Outlook for iOS </html>
We did it to ensure that whatever was changed in the email signature (by the end user) would be replaced.
For example, if an end-user adds 'John Doe', it would get replaced when he sends the email.
And if an end-user removes his/her email signature in the Settings, it will still get an email signature applied because the HTML tag is still there (but invisible).